The present invention relates generally to an electronic control system for an automotive brake system, which controls hydraulic braking pressure depending upon load condition on a vehicle for preventing vehicular wheels from locking. More specifically, the invention relates to an electronic automotive brake control system which controls proportioning rate of hydraulic pressure in distributing braking pressure built-up in a master cylinder of the brake system.
It should be noted that, throughout the disclosure, the word "load" means physical weight loaded on the vehicle by passanger or passagers riding on a vehicle and/or luggages.
Conventionally, load condition-dependent vehicular brake controls have been developed and proposed in various ways. One of the typical prior art in this field is a linkage type load-sensing proportioning valve disposed within a hydraulic circuit for rear wheel brakes. In such brake control employing the linkage type proportioning valve, a vertical displacement between a vehicle body as sprung mass and a wheel axle as unsprung mass is detected as load indicative parameter. Load corresponding to the magnitude of the detected vertical displacement, is applied to the proportioning valve for varying split point of the hydraulic braking pressure depending upon load condition of the vehicle.
However, such conventional systems could not control braking pressure distribution between front and rear wheels depending upon load distribution on each vehicular wheels.
This defect can be solved by providing variation characteristics of the split point in the proportioning valve so as to adapt braking pressure distribution to load distribution on respective vehicular wheels.